Px, Pxr (And Old Iec 60044-6, Class Tps And Old British Standard, Class X) - ABB REC670 Applications Manual

1MRK 511 401-UEN A
24.1.7.2
24.1.7.3
Bay control REC670 2.2 IEC
Application manual

E max E
ALF
EQUATION1383 V4 EN-US
Current transformers according to IEC 61869-2, class PX, PXR (and
old IEC 60044-6, class TPS and old British Standard, class X)
CTs according to these classes are specified approximately in the same way by a
rated knee point e.m.f. E
limiting secondary voltage U
corresponding E according to IEC 61869-2. It is not possible to give a general
al
relation between the E
knee
of the E . Therefore, the CTs according to class PX, PXR, X and TPS must have a
al
rated knee point e.m.f. E
» » »
E E E U
knee k kneeBS al
EQUATION2100 V2 EN-US
Current transformers according to ANSI/IEEE
Current transformers according to ANSI/IEEE are partly specified in different
ways. A rated secondary terminal voltage U
U is the secondary terminal voltage the CT will deliver to a standard burden at
ANSI
20 times rated secondary current without exceeding 10 % ratio correction. There
are a number of standardized U
CT. A corresponding rated equivalent limiting secondary e.m.f. E
estimated as follows:
= × × +
E 20 I R
alANSI sr ct
EQUATION971 V2 EN-US
where:
Z The impedance (that is, with a complex quantity) of the standard ANSI burden for the specific
bANSI
C class (W)
U The secondary terminal voltage for the specific C class (V)
ANSI
The CTs according to class C must have a calculated rated equivalent limiting
secondary e.m.f. E
alANSI
>
E maximum of E
alANSI
EQUATION1384 V2 EN-US
alreq
(E for class PX and PXR, E
knee k
for TPS). The value of the E
al
and the E but normally the E
al
that fulfills the following:
knee
(
> ×
0.8 maximum of E
alreq
ANSI
values for example, U
ANSI
= × ×
U 20 I R
ANSI sr ct
that fulfils the following:
alreq
Section 24
Requirements
for class X and the
kneeBS
is lower than the
knee
is approximately 80 %
knee
)
is specified for a CT of class C.
is 400 V for a C400
ANSI
can be
alANSI
+ × ×
20 I Z
sr bANSI
(Equation 133)
M11623-14 v5
(Equation 134)
M11623-22 v6
(Equation 135)
(Equation 136)
605